Dehumidification and the control of moisture/humidity are of extreme importance and of crucial interest in numerous industrial sectors, such as; offshore, onshore, marine and military. Several processes and techniques have been designed and developed to address this serious problem. Some of these HVAC (Heating Ventilation and Air-Conditioning) hybrid systems which perform humidity control within specific spaces, do so primarily by using temperature; heating and expanding the air's capability to absorb and retain moisture, thus lowering the relative humidity and then by cooling the air temperature below its dew point, condensing and extracting the moisture/water vapors. Conventional systems, such as the basic cooling systems are comprised of cooling coils, a condenser coil, ventilation fan and a compressor unit.
While these systems are widely used and may operate effectively in various conditions, their main function and design purpose is to climatise and provide heating and cooling of a specific area, with dehumidification as a byproduct result. These type systems are generally used in various sites and conventional as well as hazardous industrial location applications. The primary advantage of using these type systems is that they do not generate hot airstreams or operate within high temperatures which could potentially ignite or spark flammable vapors and or even volatile gases found within the ambient air.
These cooling systems are generally very efficient while operating in warmer humid climatic conditions mostly found in the southern hemisphere but are found to be inefficient and non-compatible when operating in colder, damp climatic conditions located in hazardous, volatile environments found in northern regions. The desiccant dehumidification system operates on a completely different premise, which is that of differential vapor pressures and water vapor depression. The greater the dampness and humidity in the air, the greater the water vapor concentration and pressure.
In comparison, a dry desiccant rotor found in a desiccant based dehumidification system has a very low water vapor pressure. When damp humid high vapor pressure air molecules come in contact with the desiccant rotor's surface low vapor pressure, the molecules move from high to low in an attempt to achieve equilibrium. As the wet damp airstream passes through the rotor, the molecules are retained by the desiccant material and the resulting discharge air is delivered dry. Given that the desiccant dehumidification system does not utilize liquid condensate or gases, it allows this system the capability to effectively continue to operate and remove water vapors/moisture even when the dew point air temperature drops below freezing. Therefore, the desiccant dehumidification performance actually improves in colder temperatures and is not affected by the same deficiencies/drawbacks usually found in conventional cooling-based and or hybrid systems which utilize combinations of heating and cooling stages during operation.
The desiccant dehumidification systems are equipped with a desiccant rotor which is pierced and impregnated with a desiccant type material. The system includes two operational yet segregated sections; a process section and a reactivation section. During regular operation, an ambient airstream flows through the process section and subsequently the desiccant rotor, where the moisture is collected and removed from the airstream. The resultant is dry air discharge which is then delivered into the area or enclosure to be dehumidified. Simultaneously, another airstream passes through the desiccant dehumidifier and flows in the opposite direction through the segregated reactivation section and subsequently through the rotor's desiccant material. This air stream passing through the reactivation section is heated approximately 200 to 250 degrees F., prior to coming in contact with the rotors' surface. Heat has the effect of deactivating the desiccant material in the rotor, which in turn allows the material to release the water vapor molecules into the discharge airstream and to the outside atmosphere.
During the operating process, the desiccant rotor rotates slowly (approx. 8-10 rotations per minute) about its longitudinal axis. It has been established that desiccant dehumidification systems are highly effective in greatly reducing and controlling moisture and humidity in the air they are treating. Unfortunately, sometimes the energy required to operate such a system may be limited or not readily available, especially in the case of marine, offshore or remote mobile sites where these systems are required to operate.
This problem is caused by the fact that a high (heat) temperature rise in the airflow is absolutely required in the reactivation section in order to dry out the rotor desiccant material which usually translates into high energy requirements. The generating of heat is generally accomplished with the use of but not limited to the following systems; electric heating banks or elements, flame gas burners or submersible heater immersed in a fluid running through coils located in the airflow pathway that act in a way to radiate and transfer heat onto the reactivation airflow.
These methods are generally the most commonly used means to heat the desiccant dehumidification reactivation inlet airflow, so that the air temperature rises to a degree set point, before coming in contact with the rotor desiccant material. On the other hand, in the case of a typical mechanical dehumidification system where heating and or cooling processes are utilized separately or in combination such as a hybrid system, the role of the heating element is to generate heat to expand and raise the temperature of the air volume lowering the relative humidity. This airflow then goes through the refrigerant coils which rapidly cool down the airflow temperature enabling the extraction of moisture as condensate. This new “Microwave Reactivation System” is designed and intended to be installed in standard and explosion-proof dehumidification systems for operation as a high heat generating source. In the preferred embodiment, this microwave reactivation system is installed in the reactivation section of either a standard or explosion-proof desiccant dehumidification system.
This microwave reactivation system produces heat by generating electromagnetic waves which passes through materials and fluids, causing the molecules within to rapidly oscillate in excitation and in turn generating heat.
In the preferred embodiment, the medium used to store and transmit this heat is a fluid. This fluid is moved by means of supply and return pumps, flowing through a first parallel series of glass ceramic coils which is part of a closed-loop circuit, passing through the microwave heating chamber where the fluid molecules are treated and exposed to electromagnetic waves causing excitation and generating high heat. This super heated fluid then flows through a second parallel series of metallic coils located in the lower reactivation section, in the direct path of the airflow. This heat transfer from the fluid to the coils substantially raises the temperature of the airflow as it comes in contact and passes across the surface of the coils. This heated airflow is then used to deactivate the perforated desiccant material which is impregnated within the desiccant wheel/rotor, as it passes through it. This heat laden airstream has a demagnetizing effect on the desiccant material enabling it to release the retained accumulated moisture and thus greatly lowering the vapor pressure in the desiccant material for reuse in the dehumidification process section. In an alternative embodiment, the microwave reactivation system can also be adopted and installed in any mechanical heating/cooling hybrid or refrigerant type dehumidification system that must generate a heat source in order to successfully accomplish the dehumidification process.
In the above types of dehumidification systems which are included but not limited to, a heat source is required in order to raise the intake ambient airflow temperature, expand air volume and then allow the refrigerant cooling coils to rapidly cool down the processed airflow as it passes through, so that the suspended moisture can be extracted through condensation.
Essentially, the microwave reactivation system can replace other conventional heat generating sources as previously mentioned but not limited to, such as; electric heating banks and elements, flame gas burner or submersible heating element immersed in a fluid which raises the temperature producing heat. The installation and operation of this microwave reactivation system will enable the capability to achieve the heat generating requirements which are essential for operational efficiency and optimum output of the mechanical hybrid, refrigerant and particularly the desiccant dehumidification type processes. Simultaneously, due to its highly effective ratio of low energy requirement versus high heat generating capabilities, the microwave reactivation heating system will substantially diminish the electrical power demand and consumption without compromising on performance. It is essential for these industrial dehumidification systems and in particular for the desiccant dehumidification system whether standard or explosion-proof rated, to develop proper BTU heat generation for optimum dehumidification and peak operational performance. The microwave reactivation heating system enables to safely and effectively achieve and surpass all of the above requirements.